All of the known binding systems have the main disadvantage that they are not adjustable to correspond to the different requirements. For example, it is not possible with the prior art binders to exchange as required from office bindings into official bindings or visa versa. For this purpose, different types of binders have to be fabricated so as to be able to incorporate the different fastenings and a large assortment must be kept in storage. Also, it is not possible, without difficulty, to change from a two-hole system to a four-hole system or visa versa.
Another disadvantage of the known binding systems is that the threading prongs have to be pulled by hand in order to fasten the material to be inserted, so that they wrap tightly around the fastening edge and so prevent any undesirable penetration of the material to be fastened. Furthermore, it is always necessary, if a bend-free turning of the pages is desired, to enlarge by hand the loop width of the threading system after the binder is opened in such a way that the bound edge of the pages receives a sufficiently large range of movement. The operation of the known binding systems, therefore, is time consuming and troublesome. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a binding system which can be applied to a binder at small cost and can be at any time adjusted to the different fastening-hole arrangements.
Another object of this invention is the provision of an office binder that can be changed to an official binder or visa versa.
A further object of the present invention is the provision of a ring-book-type binder for paper filing, which during opening and closing of the binder, an enforced movement by the binding prongs is achieved. The threading prongs during closure are forcibly reduced in loop size, so that with a filing material pile, formed loops surround narrowly the fastening edge of the material to be fastened and so maintain the material firmly against penetration towards the open edge of the binder; during opening of the binder, the loop width, however, is also forcibly enlarged, so that the fastened pages may be turned over individually but also in groups without a bending of the material at the fastened side resulting.
It is another object of the instant invention to provide a binding system of the type described previously, in which the complex problem is solved simply in such a way that every threading prong is in connection with the two covers of the binder, and with the free parts directed away from the back of the binder engages the connecting parts in longitudinal displacement by forming a loop.
A still further object of the invention is the provision of a binder in which, since the prongs are not fastened to the two covers of the binder, but are guided in a longitudinally displaceable manner, and in which the binding system may be easily adjusted to any desired requirements, i.e., the binders can at any time be changed from office use to official paper filing and changed from a two-hole system to a four-hole system and visa versa.